Recording medium, method and apparatus for recording, and method and apparatus for reproducing

ABSTRACT

In a recording medium which is circular and has first and second recording layers, the first and second recording layers each include one or more first tracks extending concentrically or spirally and one or more second tracks extending concentrically or spirally, each of the one or more first tracks and the one or more second tracks includes a plurality of first sectors and a plurality of second sectors, each of the plurality of first sectors includes first and second regions, each of the plurality of second sectors includes third and fourth regions, first and second grooves are formed in each of the second and fourth regions, the first and second grooves extending concentrically or spirally and oscillating sinusoidally, oscillation of the first groove has a first oscillation characteristic at a first prescribed position in the second region, oscillation of the second groove has a second oscillation characteristic at a second prescribed position in the fourth region, and the first and second oscillation characteristics are different from each other.

This application is a continuation of U.S. patent application Ser. No.10/221,329, filed on Sep. 10, 2002, which is hereby incorporated hereinby reference in its entirety.

TECHNICAL FIELD

The present invention relates to a recording medium on/from whichinformation is recorded/reproduced when irradiated with a light beam,and particularly to a multilayered optical disk having a plurality oflaminated recording layers on/from which information isrecorded/reproduced when irradiated with a light beam from a specificsurface of the disk.

BACKGROUND ART

Recently, a variety of optical disks on/from which a large quantity ofinformation can be recorded/reproduced have been developed. An exampleof large capacity optical disks is a double-sided optical disk in whichtwo optical disk pieces are attached together and information can berecorded/reproduced on/from either side of the disk. However, in thefield which frequently requires random access, for example, recordingmediums for use with computers or game machines, there is a demand thatthe optical disk has a large recording capacity while any data in thedisk can be accessed without turning the disk over.

Therefore, as an optical disk on which a large quantity of data can berecorded and in which random access can be performed, a multilayeredoptical disk in which there are two or more recording layers andinformation can be recorded/reproduced on/from one side of the disk hasbeen suggested. FIG. 29 shows an example of such a disk.

FIG. 29 is a cross-sectional view of an optical disk 2300 having tworecording layers. In FIG. 29, reference numerals 2101 and 2102respectively denote transparent first and second substrates ofpolycarbonate or the like, reference numeral 2103 denotes a firstrecording layer, reference numeral 2104 denotes a semitransparentreflection film which transmits or reflects a laser beam incident on thefirst substrate 2101, reference numeral 2105 denotes a second recordinglayer, reference numeral 2106 denotes a reflection film which reflects alaser beam 2301 incident on the first substrate 2101, and referencenumeral 2107 denotes an adhesive for attaching the substrates 2101 and2102 which has the property of transmitting light. This structure makesit possible to perform a recording/reproducing operation on either ofthe recording layers 2103 or 2105 with the laser beam 2301 incident onthe disk from the side of the substrate 2101.

Next, FIG. 30 is referenced. FIG. 30 is a diagram illustrating opticalcharacteristics of the optical disk 2300 having the two recording layers2103 and 2105 shown in FIG. 29. Here, a phase change material isconsidered to be used for the recording layers. A recording operation onthe phase change material is performed by irradiating a disk beingrotating with a light beam from a semiconductor laser so as to heat andresolve a recording layer of the disk. The temperature that therecording layer reaches and a process for cooling the recording layervary depending on the strength of intensity of the light beam, therebycausing a phase change in the recording layer.

When the intensity of the light beam is strong, the recording layer israpidly cooled from its high temperature state so as to be brought intoan amorphous state, and when the intensity of the light beam isrelatively weak, the recording layer is gradually cooled from a middleor high temperature state so as to be crystallized. Portions which arebrought into the amorphous state are generally referred to as a mark,and crystallized portions between marks are generally referred to as aspace. Binarized information is recorded on the mark and space. In thereproducing operation, the recording layer is irradiated with a weaklight beam to such an extent as not to undergo a phase change and adifference in quantity of reflection light between the mark and spaceportions is detected so as to obtain a reproduced signal.

As shown in FIG. 30, the first recording layer 2103 is designed suchthat the occupancy of a transmission coefficient is high, i.e., a hightransmission coefficient design, and the second recording layer 2105 isdesigned such that the occupancy of an absorption coefficient is high,i.e., a high absorption coefficient design. In this manner, generally inthe dual-layer optical disk having two recording layers, the first andsecond recording layers 2103 and 2105 have different characteristics.

As described above, since the recording layer characteristics of thefirst and second recording layers 2103 and 2105 are different, optimalrecording/reproducing conditions of the first and second recordinglayers are different. As an example, the reproducing condition of thesecond recording layer 2105 is described.

In general, in order to record/reproduce data, a recordable optical diskrequires data management for each sector, regardless of a single-layerdisk or a multilayered disk. Therefore, it often happens that guidinggrooves for a tracking operation of a servo means are formed in a diskproduction process and along with this, address information of sectorsis formed as pits. A sector structure of the second substrate 2102 ofthe dual-layer optical disk is illustrated in FIG. 31.

In FIG. 31, reference numeral 2102 denotes a second substrate, referencenumeral 2302 denotes a groove track, reference numeral 2301 denotes aland track between grooves, reference numeral 2303 denotes an addressregion including concave and convex pits, reference numeral 2304 denotesa data region, and the address regions 2303 and the data regions 2304are provided in both the land track 2301 and the groove track 2302.

Next, FIG. 32 is referenced. FIG. 32 provides more detailed illustrationof the vicinity of the address region 2303 of the second substrate 2102.As illustrated in FIG. 32, the groove track 2302 sinusoidally oscillatesat a constant frequency and the address regions 2303 are provided inboth the land track 2301 and the groove track 2302. The address region2303 is a region exclusively used for reproduction and is usually in acrystal state. This results from the fact that the opticalcharacteristic of the recording layer is unstable immediately after therecording layer is formed, and therefore the address region 2303 and thedata region 2304 are irradiated with a laser beam so as to be broughtinto a uniform crystal state.

In the case of reproducing data from the address region 2303 of such adual-layer optical disk 2300, when the data is reproduced from the firstrecording layer 2013, as illustrated in FIG. 30, since the firstrecording layer 2013 has a reflection coefficient of 10% at the crystalstate, up to 10% of the quantity of light returns to a photodetector.However, when the data is reproduced from the second recording layer2015, the light is required to pass through the first recording layer2013 having a transmission coefficient of 50% in both directions, andtherefore, in fact, only 3.75% of the quantity of the light returns tothe photodetector, although the reflection coefficient of the secondrecording layer 2105 is 15%, which is greater than that of the firstrecording layer. Accordingly, in order to reproduce data from theaddress region at an equivalent signal-to-noise ratio, irradiation powerof a light beam in the case of reproducing data from the secondrecording layer 2105 is required to be set so as to be larger than thatof the light beam in the case of reproducing data from the firstrecording layer 2103. However, in the case where the irradiation powercapable of reproducing data from the second recording layer 2105 ispreset, when a focusing operation of a servo means or a trackingoperation of the servo means is erroneously performed on the firstrecording layer 2013, there is a risk that data recorded on the firstrecording layer 2013 might be erased due to the excessively largeirradiation power.

On the contrary, in the case of setting the irradiation powersufficiently small as to reproduce data from the first recording layer2013, when the address information cannot be reproduced, there is a riskin determining that the servo means is performing an operation on thesecond recording layer 2105 and immediately increasing the irradiationpower. This is because there are some cases where the servo means isactually performing an operation on the first recording layer 2013,rather than the second recording layer 2105. Therefore, it is necessaryto check on a number of things, such as optimization of the reproducingconditions, reproducing operations on a plurality of regions, etc.,before increasing the irradiation power.

Further, it is not possible to securely discriminate between the firstand second recording layers 2013 and 2015 by observing a focus errorsignal or a focus sum signal in which two elemental signals included inthe focus error signal. As described above, when there is a differencebetween the first and second recording layers 2013 and 2015 with respectto the irradiation power used for a reproducing operation, it isnecessary to discriminate between the first and second recording layers2013 and 2015 more securely.

An objective of the present invention is to provide a recording mediumin which a plurality of recording layers are securely identified in ashort period of time.

DISCLOSURE OF THE INVENTION

In a recording medium which is circular and has first and secondrecording layers according to the present invention, the first andsecond recording layers each include first and second tracks extendingconcentrically or spirally, the first and second tracks each includefirst and second sectors, the first sector includes first and secondregions, the second sector includes third and fourth regions, first andsecond grooves are formed in each of the second and fourth regions, thefirst and second grooves extending concentrically or spirally andoscillating sinusoidally, oscillation of the first groove has a firstoscillation characteristic at a first prescribed position in the secondregion, oscillation of the second groove has a second oscillationcharacteristic at a second prescribed position in the fourth region, andthe first and second oscillation characteristics are different from eachother. Thus, the above-described objective is achieved.

The first oscillation characteristic may include a first phase and thesecond oscillation characteristic may include a second phase.

The first and second phases may be different from each other bysubstantially 180 degrees.

The oscillations of the first and second grooves may respectively have aminimum amplitude at the first and second prescribed positions.

The oscillations of the first and second grooves may respectively have amaximum amplitude at the first and second prescribed positions.

Readout light may be incident on the first and second recording layersfrom the same incident surface.

The first track may further include a third sector, the second track mayfurther include a fourth sector, the first region included in the firstsector may be a first address region, the third region included in thesecond sector may be a second address region, the third sector mayinclude a third address region, the fourth sector may include a fourthaddress region, the first and third sectors may form a first addressblock, the second and fourth sectors may form a second address block,the first address block may have first address information representingan address of the first address block, the first address information maybe formed by combining a first code recorded in the first address regionand a second code recorded in the third address region, the secondaddress block may have second address information representing anaddress of the second address block, and the second address informationmay be formed by combining a third code recorded in the second addressregion and a fourth code recorded in the fourth address region.

The first oscillation characteristic may include a first cycle and thesecond oscillation characteristic may include a second cycle.

Readout light may be incident on the first and second recording layersfrom the same incident surface, a distance between the first recordinglayer and the incident surface may be greater than a distance betweenthe second recording layer and the incident surface, and the first cyclemay be greater than the second cycle.

The first oscillation characteristic may include a first amplitude andthe second oscillation characteristic may include a second amplitude.

Readout light may be incident on the first and second recording layersfrom the same incident surface, a distance between the first recordinglayer and the incident surface may be greater than a distance betweenthe second recording layer and the incident surface, and the firstamplitude may be greater than the second amplitude.

The first region may include an address region in which informationrepresenting an address of the first sector is recorded and the thirdregion may include an address region in which information representingan address of the second sector is recorded.

The first region may include a first pit region representing an end ofthe first sector and the third region may include a second pit regionrepresenting an end of the second sector.

The first groove may have a first inner circumference sidewall formed onan inner circumference side of the recording medium and a first outercircumference sidewall formed on an outer circumference side of therecording medium, the second groove may have a second innercircumference sidewall formed on the inner circumference side of therecording medium and a second outer circumference sidewall formed on theouter circumference side of the recording medium, the first pit regionmay be provided at on the side surface of the first inner circumferencesidewall, and the second pit region may be provided on the side surfaceof the second outer circumference sidewall.

In a recording medium which is circular and has first and secondrecording layers according to the present invention, the first andsecond recording layers each include first and second tracks extendingconcentrically or spirally, the first and second tracks each includefirst and second sectors, the first and second sectors each includefirst and second pit regions respectively representing ends of the firstand second sectors and first and second data regions, first and secondgrooves are formed in each of the first and second data regions, thefirst and second grooves extending concentrically or spirally andoscillating sinusoidally, the first groove includes a first innercircumference sidewall formed at an inner circumference side and a firstouter circumference sidewall formed at an outer circumference side, thesecond groove includes a second inner circumference sidewall formed atthe inner circumference side and a second outer circumference sidewallformed at the outer circumference side, the first pit region is providedon the side surface of the first inner circumference sidewall, and thesecond pit region is provided on the side surface of the second outercircumference sidewall. Thus, the above-described objective is achieved.

In a reproducing apparatus for reproducing data from a recording mediumwhich is circular and has first and second recording layers according tothe present invention, the first and second recording layers eachinclude first and second tracks extending concentrically or spirally,the first and second tracks each include first and second sectors, thefirst sector includes first and second regions, the second sectorincludes third and fourth regions, first and second grooves are formedin each of the second and fourth regions, the first and second groovesextending concentrically or spirally while oscillating sinusoidally,oscillation of the first groove has a first oscillation characteristicat a first prescribed position in the second region, oscillation of thesecond groove has a second oscillation characteristic at a secondprescribed position in the fourth region, the first and secondoscillation characteristics are different from each other, and thereproducing apparatus includes: an optical head for irradiating therecording medium with a laser beam and receiving light reflected fromone of the first and second grooves so as to generate an electric signalcorresponding to the reflection light; a signal generation means forgenerating a tracking error signal and a reproduced signal based on theelectric signal; a signal process means for processing the reproducedsignal; a wobble signal extraction means for extracting a wobble signalfrom the tracking error signal; and a discrimination means fordiscriminating, based on the wobble signal, whether the reflection lightis light reflected from the first groove or light reflected from thesecond groove. Thus, the above-described objective is achieved.

The first oscillation characteristic may include a first phase and thesecond oscillation characteristic may include a second phase.

The first and second phases may be different from each other bysubstantially 180 degrees.

The oscillations of the first and second grooves may respectively have aminimum amplitude at the first and second prescribed positions.

The oscillations of the first and second grooves may respectively have amaximum amplitude at the first and second prescribed positions.

Readout light may be incident on the first and second recording layersfrom the same incident surface.

The first track may further include a third sector, the second track mayfurther include a fourth sector, the first region included in the firstsector may be a first address region, the third region included in thesecond sector may be a second address region, the third sector mayinclude a third address region, the fourth sector may include a fourthaddress region, the first and third sectors may form a first addressblock, the second and fourth sectors may form a second address block,the first address block may have first address information representingan address of the first address block, the first address information maybe formed by combining a first code recorded in the first address regionand a second code recorded in the third address region, the secondaddress block may have second address information representing anaddress of the second address block, and the second address informationmay be formed by combining a third code recorded in the second addressregion and a fourth code recorded in the fourth address region.

The first oscillation characteristic may include a first cycle and thesecond oscillation characteristic may include a second cycle.

Readout light may be incident on the first and second recording layersfrom the same incident surface, a distance between the first recordinglayer and the incident surface may be greater than a distance betweenthe second recording layer and the incident surface, and the first cyclemay be greater than the second cycle.

In a reproduction method for reproducing data from a recording mediumwhich is circular and has first and second recording layers according tothe present invention, the first and second recording layers eachinclude first and second tracks extending concentrically or spirally,the first and second tracks each include first and second-sectors, thefirst sector includes first and second regions, the second sectorincludes third and fourth regions, first and second grooves are formedin each of the second and fourth regions, the first and second groovesextending concentrically or spirally and oscillating sinusoidally,oscillation of the first groove has a first oscillation characteristicat a first prescribed position in the second region, oscillation of thesecond groove has a second oscillation characteristic at a secondprescribed position in the fourth region, the first and secondoscillation characteristics are different from each other, and thereproduction method includes the steps of: irradiating the recordingmedium with a laser beam and receiving light reflected from one of thefirst and second grooves so as to generate an electric signalcorresponding to the reflection light; generating a tracking errorsignal and a reproduced signal based on the electric signal; processingthe reproduced signal; extracting a wobble signal from the trackingerror signal; and discriminating, based on the wobble signal, whetherthe reflection light is light reflected from the first groove or lightreflected from the second groove. Thus, the above-described objective isachieved.

In a recording apparatus for recording data on a recording medium whichis circular and has first and second recording layers according to thepresent invention, the first and second recording layers each includefirst and second tracks extending concentrically or spirally, the firstand second tracks each include first and second sectors, the firstsector includes first and second regions, the second sector includesthird and fourth regions, first and second grooves are formed in each ofthe second and fourth regions, the first and second grooves extendingconcentrically or spirally and oscillating sinusoidally, oscillation ofthe first groove has a first oscillation characteristic at a firstprescribed position in the second region, oscillation of the secondgroove has a second oscillation characteristic at a second prescribedposition in the fourth region, the first and second oscillationcharacteristics are different from each other, and the recordingapparatus includes: an optical head for irradiating the recording mediumwith a laser beam and receiving light reflected from one of the firstand second grooves so as to generate an electric signal corresponding tothe reflection light: a signal generation means for generating atracking error signal and a reproduced signal based on the electricsignal: a wobble signal extraction means for extracting a wobble signalfrom the tracking error signal; a discrimination means fordiscriminating, based on the wobble signal, whether the reflection lightis light reflected from the first groove or light reflected from thesecond groove; and a recording signal generation means for generating arecording signal, wherein the optical head records the recording signalgenerated by the recording signal generation means on the recordingmedium. Thus, the above-described objective is achieved.

In a recording method for recording data on a recording medium which iscircular and has first and second recording layers according to thepresent invention, the first and second recording layers each includefirst and second tracks extending concentrically or spirally, the firstand second tracks each include first and second sectors, the firstsector includes first and second regions, the second sector includesthird and fourth regions, first and second grooves are formed in each ofthe second and fourth regions, the first and second grooves extendingconcentrically or spirally and oscillating sinusoidally, oscillation ofthe first groove has a first oscillation characteristic at a firstprescribed position in the second region, oscillation of the secondgroove has a second oscillation characteristic at a second prescribedposition in the fourth region, the first and second oscillationcharacteristics are different from each other, and the recording methodincludes the steps of: irradiating the recording medium with a laserbeam and receiving light reflected from one of the first and secondgrooves so as to generate an electric signal corresponding to thereflection light; generating a tracking error signal based on theelectric signal; extracting a wobble signal from the tracking errorsignal; discriminating, based on the wobble signal, whether thereflection light is light reflected from the first groove or lightreflected from the second groove; generating a recording signal; andrecording the generated recording signal on the recording medium. Thus,the above-described objective is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural diagram of an optical disk according toEmbodiment 1 of the present invention.

FIG. 2 is a plan view of a first substrate included in the optical diskaccording to Embodiment 1.

FIG. 3 is a plan view of a second substrate included in the optical diskaccording to Embodiment 1.

FIG. 4 is a diagram for explaining the oscillation of grooves- formed inthe optical disk according to Embodiment 1.

FIG. 5 is a block diagram of a recording/reproducing apparatus accordingto Embodiment 1.

FIG. 6 is a flowchart for discriminating substrates according toEmbodiment 1.

FIG. 7 is a diagram for explaining wobble signals according toEmbodiment 1.

FIG. 8 is a diagram for explaining a method for reproducing data from anaddress region according to Embodiment 1.

FIG. 9 is a diagram for explaining a method for detecting whether or notany discontinuous portion is present according to Embodiment 1.

FIG. 10 is a diagram for explaining the oscillation of grooves formed inanother optical disk according to Embodiment 1.

FIG. 11 is a diagram for explaining the oscillation of grooves formed instill another optical disk according to Embodiment 1.

FIG. 12 is a diagram for explaining the oscillation of grooves formed instill another optical disk according to Embodiment 1.

FIG. 13 is a diagram for explaining the oscillation of grooves formed instill another optical disk according to Embodiment 1.

FIG. 14 is a diagram for explaining the oscillation of grooves formed instill another optical disk according to Embodiment 1.

FIG. 15 is a diagram for explaining the oscillation of grooves formed instill another optical disk according to Embodiment 1.

FIG. 16 is a structural diagram of an optical disk according toEmbodiment 2 of the present invention.

FIG. 17 is a plan view of a first substrate included in the optical diskaccording to Embodiment 2.

FIG. 18 is a plan view of a second substrate included in the opticaldisk according to Embodiment 2.

FIG. 19 is a diagram for explaining the oscillation of grooves formed inthe optical disk according to Embodiment 2.

FIG. 20 is a block diagram of a recording/reproducing apparatusaccording to Embodiment 2.

FIG. 21 is a flowchart for discriminating substrates according toEmbodiment 2.

FIG. 22 is a diagram for explaining wobble signals according toEmbodiment 2.

FIG. 23 is a diagram for explaining the oscillation of grooves formed inanother optical disk according to Embodiment 2.

FIGS. 24-28 are diagrams each explaining the oscillation of groovesformed in still another optical disk according to Embodiments 1 and 2.

FIG. 29 is a cross-sectional view of an optical disk described in aconventional example.

FIG. 30 is a diagram for explaining optical characteristics of anoptical disk.

FIG. 31 is a plan view of a substrate included in a conventional opticaldisk.

FIG. 32 is a diagram for explaining the oscillation of grooves formed inthe conventional optical disk.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a recording medium according to embodiments of the presentinvention will be described with reference to the drawings.

Embodiment 1

FIG. 1 is a structural diagram of an optical disk 100 according toEmbodiment 1 of the present invention. In FIG. 1, the optical disk 100includes a first substrate 101, a first recording layer 102, an adhesiveresin 103, a second recording layer 104 and a second substrate 105. Thefirst substrate 101, the first recording layer 102, the adhesive resin103, the second recording layer 104 and the second substrate 105 havetheir respective clamp holes 106. The first recording layer 102 includesa lead-in region 107 and a recording region 108. The second recordinglayer 104 includes a lead-in region 109 and a recording region 110. Thefirst and second substrates 101 and 105 are formed of a polycarbonateresin or the like and respectively protect the first and secondrecording layers 102 and 104.

Next, FIG. 2 is referenced. FIG. 2 illustrates a sector structure on thefirst substrate 101 included in the optical disk 100 shown in FIG. 1.The first substrate 101 is provided with groove tracks 202 and landtracks 201 which are formed between the groove tracks 202. The groovetracks 202 and the land tracks 201 spirally extend and sinusoidallyoscillate (hereinafter, the sinusoidal oscillation is referred to as“wobbling”). Information is recorded on both the groove tracks 202 andthe land tracks 201, and each of the groove tracks 202 and the landtracks 201 includes one or more address regions 203 and a data region204.

When each of the groove tracks 202 and the land tracks 201 is dividedinto a plurality of sectors, an address region 203 and a data region 204are allocated to each sector. In this case, each address region 203 isalso referred to as a sector address region. With respect to a trackstructure, the land tracks 201 and the groove tracks 202 can becontinuously and spirally connected to each other every other circuit.

Next, FIG. 3 is referenced. FIG. 3 illustrates a sector structure on thesecond substrate 105 included in the optical disk 100 shown in FIG. 1.The second substrate 105 is provided with groove tracks 302 and landtracks 301 which are formed between the groove tracks 302. The groovetracks 302 and the land tracks 301 extend and wobble. Information isrecorded on both the groove tracks 302 and the land tracks 301, and eachof the groove tracks 302 and the land tracks 301 includes one or moreaddress regions 303 and a data region 304.

When each of the groove tracks 302 and the land tracks 301 is dividedinto a plurality of sectors, an address region 303 and a data region 304are allocated to each sector. In this case, each address region 303 isalso referred to as a sector address region. With respect to a trackstructure, the land tracks 301 and the groove tracks 302 can becontinuously and spirally connected to each other every other circuit.

Next, FIG. 4 is referenced. FIG. 4 provides more detailed illustrationof the vicinity of the address region 203 of the first substrate 101 andthe vicinity of the address region 303 of the second substrate 105. Theaddress regions 203 each representing an address of a sector areallocated to the groove tracks 202 and the land tracks 201, and theaddress regions 303 each representing an address of a sector areallocated to the groove tracks 302 and the land tracks 301. As shown inFIG. 4, in the first substrate 101, a phase of the oscillation of eachgroove track 202 at a start position 401 in the data region 204 is atzero degrees.

On the other hand, as shown in FIG. 4, in the second substrate 105, aphase of the oscillation of each groove track 302 at a start position402 in the data region 304 is at 180 degrees. That is, in the first andsecond substrates 101 and 105, phases of the oscillation of the tracksat the start positions 401 and 402 in the data regions are differentfrom each other. By detecting the difference in the phase of theoscillation, it is possible to securely discriminate whether the servomeans is performing an operation for controlling a light beam on thefirst or second substrates 101 or 105 in a short period of time.

Next, a method for detecting a difference in the phase of theoscillation is described with reference to FIG. 5. FIG. 5 is a blockdiagram of a recording/reproducing apparatus 500 forrecording/reproducing data on/from the optical disk 100 shown in FIG. 1.

In FIG. 5, the recording/reproducing apparatus 500 includes: an opticalhead 502 for irradiating the optical disk 100 shown in FIG. 1 withlight; a signal generation circuit 503 for generating a tracking errorsignal and a focus error signal; a signal process circuit 504 forprocessing a reproduced signal; a recording signal generation circuit512 for generating a recording signal; a motor 505 for rotating theoptical disk 100; a servo means 506 for controlling the optical head 502and the motor 505; a wobble signal extraction circuit 507 for extractinga wobble signal which appears in the tracking error signal; a wobblepolarity discrimination means 508 for discriminating the polarity of awobble extracted by the wobble signal extraction circuit 507; asubstrate discrimination means 509 for discriminating whether the servomeans is performing an operation on either the first or second substrateaccording to a result provided by the wobble polarity discriminationmeans 508; a reference clock generation means 510 for providing clock tothe servo means 506 and the wobble polarity discrimination means 508;and an irradiation power control means 511 for controlling irradiationpower.

The operation of the recording/reproducing apparatus 500 is describedbelow with reference to FIG. 5. The optical disk 100 is rotated by themotor 505, and the servo means 506 controls the optical head 502 so asto focus a laser beam on the optical disk 100 for scanning the tracksspirally formed on the optical disk 100. In this case, the irradiationpower is set by the irradiation power control means 511 so as to beequivalent to a lower one of the irradiation power for reproducing datafrom the first recording layer 102 (FIG. 1) and the irradiation powerfor reproducing data from the second recording layer 104 (FIG. 1). Itshould be noted that the optical characteristics of the optical disk 100are as shown in FIG. 25 and in Embodiment 1, the irradiation power forreproducing data from the first recording layer 102 is lower than thatfor reproducing data from the second recording layer 104.

The signal generation circuit 503 receives from the optical head 502 anelectric signal corresponding to light reflected from the optical disk100, thereby generating a focus error signal representing a light focusstate of a laser beam on the optical disk 100, a tracking error signalrepresenting a scanning state of tracks of the optical disk 100 and areproduced signal of data recorded on the optical disk 100. Thereproduced signal is demodulated by the signal process circuit 504 so asto reproduce data. Further, both the focus error signal and the trackingerror signal are input to the servo means 506, and the servo means 506controls the optical head 502 so as to realize the optimal light focusstate and track scanning state.

The tracking error signal is also input to the wobble signal extractioncircuit 507, and the wobble signal extraction circuit 507 extracts awobble signal from the tracking error signal on which a signal recordedin an address region is also superimposed by means of a band-passfilter, which passes wobble components therethrough, and a binarizingcircuit.

The wobble polarity discrimination means 508 uses the reference clock ata fixed frequency generated by the reference clock generation means 510so as to discriminate the wobble polarities at the start positions 401and 402 (FIG. 4) in the data regions 204 and 304 (FIG. 4) based on thewobble signal extracted by the wobble signal extraction circuit 507. Thereference clock generation means 510 includes, for example, a quartzoscillator. Discrimination of the wobble polarities of, for example, abinarized wobble signal, can be realized using the reference clock so asto count the time period required for the binarized signal to rise froma prescribed position in the address region 204 or 304. The substratediscrimination means 509 observes a signal output by the wobble polaritydiscrimination means 508 so as to discriminate whether the servo meansis performing an operation on the first or second substrate 101 or 105.

The recording signal generation circuit 512 generates a recording signalfor recording data on the optical disk 100. The optical head 502 recordsa recording signal generated by the recording signal generation circuit512 on either data region 204 or 304 of the optical disk 100.

A flow of the substrate discriminating operation is further describedwith reference to a flowchart of FIG. 6. Firstly, once the power of therecording/reproducing apparatus 500 is turned on when the optical disk100 is being inserted thereinto or in a state where the optical disk 100has been inserted thereinto (S601), the optical head 502 is moved to thevicinity of an innermost circumference of the recording region 108 or110, and the motor 505 is rotated at a prescribed rotation speed so asto rotate the optical disk 100 (S602). Next, the optical head 502 ismade to emit a laser beam (S603), focus control is turned on so as tofocus the laser beam on the first or second substrates 101 or 105(S604). Further, tracking control is turned on so as to scan a groovetrack or a land track on the first or second substrate 101 or 105 withthe laser beam (S605).

In this state, a signal including wobble components shown in FIG. 7appears in a tracking error signal. In FIG. 7, reference numeral 701denotes a tracking error signal when the servo means is performing anoperation on the first substrate 101, and reference numeral 703 denotesa tracking error signal when the servo means is performing an operationon the second substrate 105. In the wobble signal extraction circuit507, the band-pass filter performs bandwidth limiting on the trackingerror signal so as to pass frequency bandwidth components of a wobblesignal therethrough, thereby removing the other bandwidth components.

By binarizing the tracking error signal after the extraction of thewobble components, a wobble signal denoted by reference numeral 702 or704 is obtained. Reference numeral 702 denotes a wobble signal when theservo means is performing an operation on the first substrate 101, andreference numeral 704 denotes a wobble signal when the servo means isperforming an operation on the second substrate 105. The wobble polaritydiscrimination means 508 uses the reference clock so as to count timeperiod 705 or 706 required for the binarized signal to rise from aprescribed position 708 in the address region (S606). In this case, whena wobble cycle 707 is equivalent to, for example, 120 counts of thereference clock, as shown in FIG. 7, the time period 705 in the wobblesignal 702 is longer than the time period 706 in the wobble signal 704by 60 counts. In the case where the number of counts between theprescribed position 708 of the address region and an end position 709 ofthe address region is, for example, 160, when a threshold is 190 counts,it is possible to determine that the first substrate is being operatedon when the number of counts is equal to or more than 190 and the secondsubstrate is being the operated on when the number of counts is lowerthan 190 (S607, S608 and S609).

It should be noted that in the case where the threshold of the countvalue is sufficiently large, even when the position on which a focusingor tracking operation of the servo means is performed is slightlydeviated, it is possible to perform the discriminating operation. Inthis manner, by shifting phases of the wobbles at start positions in thedata regions of the first and second substrates so as to differ fromeach other by 180 degrees, it is possible to increase a differencebetween the theoretical number of counts and a threshold, therebyincreasing the reliability of discrimination.

In Embodiment 1, although a phase of the oscillation of the groove trackis at zero degrees at the start position in the data region 204 of thefirst substrate 101 and a phase of the oscillation of the groove trackis at 180 degrees at the start position of the data region 304 of thesecond substrate 105, the phases of the first and second substrates 101and 105 are not limited to this. The phases of the first and secondsubstrates 101 and 105 can be any phases other than those at zerodegrees and 180 degrees so long as it is possible to discriminatewhether the servo means is performing an operation on the first orsecond substrate 101 or 105.

As described above, by providing the first and second substrates so asto have different phases of the oscillation of the tracks at the startpositions of the data regions, it is possible to discriminate betweenthe first and second substrate 101 and 105 at the time a focus ortracking operation is performed by the servo means, i.e., before readingaddress information recorded in the address region, and therefore evenwhen information representing which one of the first and secondsubstrates 101 and 105 is the substrate is recorded in the lead-inregions 107 and 109 provided at the innermost circumference of the disk,it is not necessary to reproduce such information so as to discriminatebetween the first and second substrates 101 and 105. Therefore, it ispossible to shorten the time period required for reproducing data fromthe lead-in regions 107 and 109.

In this manner, by providing the first and second substrates 101 and 105so as to have different phases of the oscillation of the tracks at thestart positions of the data regions, it is possible to discriminatebetween the first or second substrates 101 or 105 at the time a focus ortracking operation is performed by the servo means, i.e., before readingaddress information recorded in the address region, and therefore it ispossible to shorten the time period required for reproducing datarecorded in the address region of the substrate on which the servo meansis performing an operation.

It should be noted that as in the case of Embodiment 1, by providing theaddress regions 203 and 303 in which the groove tracks 202 and 302respectively become discontinuous at positions where an amplitude of theoscillation is minimum, even if the tracking position is deviated whenreproducing address data recorded in the address regions 203 and 303 inwhich the groove tracks 202 and 302 respectively become discontinuous,it is possible to properly reproduce address data.

Detailed description is provided with reference to FIG. 8. In FIG. 8,reference numeral 2501 denotes a groove track or a land track. Referencenumerals 2606 and 2607 respectively denote trajectories in which lightspots 2606A and 2607A pass. The light spot 2606A passes alongsubstantially the center of the land track 2501 in the trajectory 2606and the light spot 2607A passes along the land track 2501 at a lowerside thereof on the sheet of the figure in the trajectory 2606.Reference numeral 2504 denotes an address region provided at a positionwhere an amplitude of the oscillation of the land track 2501 becomesmaximum and reference numeral 2505 denotes an address region provided ata position where the amplitude of the oscillation of the land track 2501becomes minimum.

Here, reference numerals 2502 and 2503 respectively denote electricsignals into which reflection light is converted when the trajectory2606 of the light spot 2606A and the trajectory 2607 of the light spot2607A pass along the tracks. As shown in FIG. 8, in the case where theaddress region 2505 is provided at a position where the amplitude of theoscillation becomes minimum, even if the tracking position of the lightspot is deviated so that the light spot 2607A passes in the trajectory2607, address information recorded in the address region 2505 can becorrectly reproduced. However, in the case where the address region 2504is provided at a position where the amplitude of the oscillation becomesmaximum, if the tracking position of the light spot is deviated so thatthe light spot 2607A passes in the trajectory 2607, address informationrecorded in the address region 2504 cannot be correctly reproduced.

According to the present invention, it is not necessary to reproducedata recorded in the lead-in region or the address region so as todiscriminate between the first and second substrates 101 and 105, and itis possible to set the irradiation power of a laser beam so as to beequal to or lower than the lowest irradiation power for reproducing datafrom the respective regions so long as the wobble polarities can bediscriminated, thereby eliminating the risk of damaging data recorded inthe data region or the address region.

In Embodiment 1, although an optical disk having two recording layers inwhich incident surfaces of readout light are identical to each other hasbeen described, the recording layers are not limited to two layers. Solong as at least two recording layers are available for recording, otherlayers may be used exclusively for reproducing.

Although pits are positioned in the address region according toEmbodiment 1, the positions, the number and the arrangement of the pitsmay not be limited to this.

The oscillation of grooves formed in the other optical disk is describedwith reference to FIG. 10. Each of the is groove tracks 202 and the landtracks 201 includes a sector portion 231. Each sector portion 231includes a plurality of sectors 221A, 221B and 221C. The sectors 221A,221B and 221C respectively include address regions 203A, 203B and 203C,and data regions 204A, 204B and 204C. Each of the groove tracks 302 andthe land tracks 301 include an address block 251. Each address block 251includes a plurality of sectors 241A, 241B and 241C. The sectors 241A,241B and 241C respectively include address region 303A, 303B and 303C,and data region 304A, 304B and 304C.

In the address region 203A included in the sector 221A, a pattern, whichcorresponds to a code “S” representing a synchronization mark, is formedas part of the address information. By reading the pattern correspondingto the code “S”, a position where an address block is started (a startsector position) is identified.

In the address region 203B included in the sector 221B, a patterncorresponding to a code “1” is formed as part of address information. Inthe address region 203C included in the sector 221C, a patterncorresponding to a code “0” is formed as part of the addressinformation.

In the case of FIG. 10, three sectors 221A, 221B and 221C form a singleaddress block, and from the sector 221A, the codes “S”, “1” and “0” aresequentially recorded. Therefore, address information which represents aposition of the sector portion 231 results in “S10” in which these codesare put together. Here, the identification code “S” represents a startposition of address information, two codes “1” and “0” following thecode “S” are binary information and this is substantial addressinformation representing the position of the sector portion 231. Forexample, in the case of “S10” described above, this is represented as“2” in the decimal notation, so that it is possible to identify theaddress representing the position of the sector portion 231 as being 2.

As shown in FIG. 10, in the first substrate 101, a phase of theoscillation of each of the groove tracks 202 at the respective startpositions 401A, 401B and 401C of the data regions 204A, 204B and 204C isat zero degrees.

On the other hand, in the second substrate 105, a phase of theoscillation of each of the groove tracks 302 at the respective startpositions 402A, 402B and 402C of the data regions 304A, 304B and 304C isat 180 degrees. That is, there is a difference between the first andsecond substrates 101 and 105 with respect to the phases of theoscillation of the tracks at the start positions of the data regions. Bydetecting the difference in the phase of the oscillation, it is possibleto securely discriminate whether the servo means is performing anoperation for controlling a light beam on the first or second substrate101 or 105 in a short period of time.

Further, in Embodiment 1, although tracks are discontinuously provideddue to the address regions, the address regions 203 and 303 shown inFIG. 4 are not always required so long as the start positions of thetracks are identified, and the tracks can be discontinuously provideddue to regions except for the address regions. FIG. 11 shows an examplein which pits are not present at positions where the tracks becomediscontinuous. It should be noted that in FIG. 11, recording operationsare performed only on the groove tracks.

In FIG. 11, reference numerals 801, 803, 804 and 805 denotediscontinuous portions each representing an end of a sector in the firstsubstrate. A plurality of sectors each containing information whichrepresents whether or not there is another discontinuous portion half acycle after one discontinuous portion are put together as addressinformation. For example, the discontinuous portion 802 follows thediscontinuous portion 801 but no discontinuous portion follows thediscontinuous portion 803. Reference numerals 807, 809 and 810 denotediscontinuous portions each representing an end of a sector in thesecond substrate. A plurality of sectors each containing informationwhich represents whether or not there is another discontinuous portionhalf a cycle after one discontinuous portion are put together as addressinformation. For example, the discontinuous portion 808 follows thediscontinuous portion 807 but no discontinuous portion follows thediscontinuous portion 809.

As shown in FIG. 11, a phase of the oscillation of each track at thediscontinuous portions 801, 803, 804 and 805 each representing an end ofa sector in the first substrate is at 90 degrees, and a phase of theoscillation of each track at the discontinuous portions 807, 809 and 810each representing an end of a sector in the second substrate is at 270degrees. That is, there is a difference between the first and secondsubstrates with respect to the phase of the oscillation of the tracks atthe discontinuous portions each representing an end of a sector. Bydetecting the difference in the phase of the oscillation, it is possibleto securely discriminate whether the servo means is performing anoperation for controlling a light beam on the first or secondsubstrates.

It should be noted that by providing regions in which the grooves becomediscontinuous at positions where an amplitude of the oscillation ismaximum, it is possible to increase the displacement of a tracking errorsignal, and therefore it is possible to correctly detect whether or notany discontinuous portion is present.

Detailed description is provided with reference to FIG. 9. In FIG. 9,reference numeral 2611 denotes a groove track or a land track. A lightspot 2621 substantially passes along the center of the track 2611.Reference numeral 2616 denotes an address region provided at a positionwhere an amplitude of the oscillation of the track becomes maximum andreference numeral 2615 denotes an address region provided at a positionexcept for the position where the amplitude of the oscillation of thetrack becomes maximum.

Reference numeral 2612 denotes a difference signal representing A−B inan element 2620 which converts reflection light into an electric signalwhen the light spot 2621 passes along the track 2611. It should be notedthat reference numeral 2617 denotes a light spot focused on the element2620. Reference numeral 2613 denotes an output signal when thedifference signal 2612 is input to a high-pass filter 2629. A signal2614 is a signal obtained by binarizing the signal 2613 at a prescribedslice level. The signal 2614 makes it possible to detect whether or notany discontinuous portion is present.

Here, in the case where the address region 2616 in which grooves arediscontinuous is provided at a position where an amplitude of theoscillation is maximum, it is possible to increase the quantity ofdisplacement of the difference signal 2612 can be increased as comparedto the case where the address region 2615 is provided at a positionexcept for the position where the amplitude of the oscillation ismaximum, and therefore it is possible to correctly detect whether or notany discontinuous portion is present.

Further, in Embodiment 1, although the tracks are discontinuouslyprovided due to the address regions, the address regions 203 and 303shown in FIG. 4 are not always required so long as the start positionsof the tracks are identified, and therefore the address regions may notbe present on the recording tracks. FIGS. 12, 13 and 14 show examples inwhich the address regions are not present on the recording tracks. Itshould be noted that in FIGS. 12, 13 and 14, recording operations areperformed only on the groove tracks.

In FIG. 12, reference numerals 1601, 1603, 1604 and 1605 denote pitseach representing an end of a sector in the first substrate. A pluralityof sectors each containing information which represents whether or notthere is another pit half a cycle after one pit are put together asaddress information of an adjacent groove track. For example, the pit1602 follows the pit 1601 but no pit follows the pit 1603. Further,reference numerals 1607, 1609 and 1610 denote pits each representing anend of a sector in the second substrate. A plurality of sectors eachcontaining information which represents whether or not there is anotherpit half a cycle after one pit are put together as address informationof an adjacent groove track. For example, the pit 1608 follows the pit1607 but no pit follows the pit 1609. It should be noted that aninterval between pits is not limited to half a cycle and another cyclecan be employed.

As shown in FIG. 12, a phase of the oscillation of each track at thepits 1601, 1603, 1604 and 1605 each representing an end of a sector inthe first substrate is at 90 degrees, and a phase of the oscillation ofeach track at the pits 1607, 1609 and 1610 each representing an end of asector in the second substrate is at 270 degrees. That is, there is adifference between the first and second substrates with respect to thephase of the oscillation of the tracks at the pits each representing anend of a sector. By detecting the difference in the phase of theoscillation, it is possible to securely discriminate whether the servomeans is performing an operation for controlling a light beam on thefirst or second substrate.

Further, in FIG. 13, reference numerals 1701, 1703, 1704 and 1705 denotepits each representing an end of a sector in the first substrate. Aplurality of sectors each containing information which representswhether or not there is another pit one cycle after one pit are puttogether as address information of an adjacent groove track. Forexample, the pit 1702 follows the pit 1701 but no pit follows the pit1703.

Furthermore, reference numerals 1707, 1709 and 1710 denote pits eachrepresenting an end of a sector in the second substrate. A plurality ofsectors each containing information which represents whether or notthere is another pit one cycle after one pit are put together as addressinformation of an adjacent groove track. For example, the pit 1708follows the pit 1707 but no pit follows the pit 1709. It should be notedthat an interval between pits is not limited to one cycle and anothercycle can be employed.

As shown in FIG. 13, the pits in the first substrate are located on theinner circumference side of the groove tracks and the pits in the secondsubstrate are located on the outer circumference side of the groovetracks. That is, there is a difference between the first and secondsubstrates with respect to a direction of sidewalls having pits. Bydetecting the difference, it is possible to discriminate whether theservo means is performing an operation for controlling a light beam onthe first or second substrates. With respect to the directions of thepits, the pits in the first substrate can be located on the outercircumference of the groove tracks and the pits in the second substratecan be located on the inner circumference of the groove tracks.

Further, in FIG. 14, reference numerals 1801, 1803, 1804 and 1805 denotepits each representing an end of a sector in the first substrate. Aplurality of sectors each containing information which representswhether or not there is another pit one cycle after one pit are puttogether as address information of a groove track. For example, the pit1802 follows the pit 1801 but no pit follows the pit 1803. Further,reference numerals 1807, 1809 and 1810 denote pits each representing anend of a sector in the second substrate. A plurality of sectors eachcontaining information which represents whether or not there is anotherpit one cycle after one pit are put together as address information of agroove track. For example, the pit 1809 follows the pit 1808 but no pitfollows the pit 1807. It should be noted that an interval between pitsis not limited to one cycle and another cycle can be employed.

As shown in FIG. 14, although the pits in both the first and secondsubstrates are located on the inner circumference side of the groovetracks, a phase of the oscillation of each track at the pits 1801, 1803,1804 and 1805 each representing an end of a sector in the firstsubstrate is at 90 degrees and a phase of the oscillation of each trackat the pits 1807, 1809 and 1810 each representing an end of a sector inthe second substrate is at 270 degrees. That is, there is a differencebetween the first and second substrates with respect to the phase of theoscillation of the tracks at the pits each representing an end of asector. By detecting the difference in the phase of the oscillation, itis possible to discriminate whether the servo means is performing anoperation for controlling a light beam on the first or second substrate.It should be noted that the direction of the pits are not limited tothis, and the pits can be located on the outer circumference side.

In Embodiment 1, although the first and second substrates are notdefined with respect to an oscillation amplitude of a wobble, theoscillation amplitude in the second substrate can be set so as to behigher than that in the first substrate. FIG. 15 shows an example ofsuch a case. As shown in FIG. 15, by setting an oscillation amplitude A2of the second substrate so as to be higher than an oscillation amplitudeA1 of the first substrate, it is possible to improve a signal-to-noiseratio of a wobble signal in the case where the servo means is performingan operation for controlling a light beam on the second substrate.

Embodiment 2

FIG. 16 is a structural diagram of an optical disk 1500 according toEmbodiment 2 of the present invention. In FIG. 16, the optical disk 1500includes a first substrate 901, a first recording layer 902, an adhesiveresin 903, a second recording layer 904 and a second substrate 905. Thefirst substrate 901, the first recording layer 902, the adhesive resin903, the second recording layer 904 and the second substrate 905 havetheir respective clamp holes 906. The first recording layer 902 includesa lead-in region 907 and a recording region 908. The second recordinglayer 904 includes a lead-in region 909 and a recording region 910. Thefirst and second substrates 901 and 905 are formed of a polycarbonateresin or the like and respectively protect the first and secondrecording layers 902 and 904.

Next, FIG. 17 is referenced. FIG. 17 illustrates a sector structure onthe first substrate 901 included in the optical disk 1500 shown in FIG.16. The first substrate 901 is provided with groove tracks 1002 and landtracks 1001 each being formed between the groove tracks 1002. The groovetracks 1002 and the land tracks 1001 spirally extend and sinusoidallywobble. Information is recorded on both the groove tracks 1002 and theland tracks 1001, and each of the groove tracks 1002 and the land tracks1001 includes one or more address regions 1003 and a data region 1004.

When each of the groove tracks 1002 and the land tracks 1001 is dividedinto a plurality of sectors, an address region 1003 and a data region1004 are allocated to each sector. In this case, each address region1003 is also referred to as a sector address region. With respect to atrack structure, the land tracks 1001 and the groove tracks 1002 can becontinuously and spirally connected to each other every other circuit.

Next, FIG. 18 is referenced. FIG. 18 illustrates a sector structure onthe second substrate 905 included in the optical disk 1500 shown in FIG.16. The second substrate 905 is provided with groove tracks 1102 andland tracks 1101 which are formed between the groove tracks 1102. Thegroove tracks 1102 and the land tracks 1101 extend and wobble.Information is recorded on both the groove tracks 1102 and the landtracks 1101, and each of the groove tracks 1102 and the land tracks 1101includes one or more address regions 1103 and a data region 1104.

When each of the groove tracks 1102 and the land tracks 1101 is dividedinto a plurality of sectors, an address region 1103 and a data region1104 are allocated to each sector. In this case, each address region1103 is also referred to as a sector address region. With respect to atrack structure, the land tracks 1101 and the groove tracks 1102 can becontinuously and spirally connected to each other every other circuit.

Next, FIG. 19 is referenced. FIG. 19 provides more detailed illustrationof the vicinity of the address region 1003 of the first substrate 901and the vicinity of the address region 1103 of the second substrate 905.The address regions 1003 each representing an address of a sector areallocated to the groove tracks 1002 and the land tracks 1001, and theaddress regions 1103 each representing an address of a sector areallocated to the groove tracks 1102 and the land tracks 1101. As shownin FIG. 19, a cycle of the oscillation of each groove track 1002 in thefirst substrate 901 is shorter than that of the oscillation of eachgroove track 1102 in the second substrate 905. That is, there is adifference between the first and second substrates 901 and 905 withrespect to an oscillation frequency of a track. By detecting thedifference in the oscillation frequency, whether the servo means isperforming an operation for controlling a light beam on the first orsecond substrate is discriminated.

Next, a method for detecting a difference in cycles of the oscillationis described with reference to FIG. 20. FIG. 20 is a block diagram of arecording/reproducing apparatus 1900 for recording/reproducing dataon/from the optical disk 1500 shown in FIG. 16.

In FIG. 20, the recording/reproducing apparatus 1900 includes: anoptical head 1302 for irradiating the optical disk 1500 shown in FIG. 16with light; a signal generation circuit 1303 for generating a trackingerror signal and a focus error signal; a signal process circuit 1304 forprocessing a reproduced signal; a recording signal generation circuit1312 for generating a recording signal; a motor 1305 for rotating theoptical disk 1500; a servo means 1306 for controlling the optical head1302 and the motor 1305: a wobble signal extraction circuit 1307 forextracting a wobble signal which appears in the tracking error signal; awobble cycle measurement means 1308 for measuring a cycle of a wobbleextracted by the wobble signal extraction circuit 1307; a substratediscrimination means 1309 for discriminating whether the servo means isperforming an operation on either the first or second substrateaccording to a result provided by the wobble cycle measurement means1308; a reference clock generation means 1310 for providing clock to theservo means 1306 and the wobble cycle measurement means 1308; and anirradiation power control means 1311 for controlling irradiation power.

The operation of the recording/reproducing apparatus 1900 is describedbelow with reference to FIG. 20. The optical disk 1500 is rotated by themotor 1305, and the servo means 1306 controls the optical head 1302 soas to focus a laser beam on the optical disk 1500 for scanning thetracks spirally formed on the optical disk 1500. In this case, theirradiation power is set by the irradiation power control means 1311 soas to be equivalent to a lower one of the irradiation power forreproducing data from the first recording layer 902 (FIG. 16) and theirradiation power for reproducing data from the second recording layer904 (FIG. 16). It should be noted that the optical characteristics ofthe optical disk 1500 are as shown in FIG. 25 and in Embodiment 2, theirradiation power for reproducing data from the first recording layer902 is lower than that for reproducing data from the second recordinglayer 904.

The signal generation circuit 1303 receives from the optical head 1302an electric signal corresponding to light reflected from the opticaldisk 1500, thereby generating a focus error signal representing a lightfocus state of a laser beam on the optical disk 1500, a tracking errorsignal representing a scanning state of tracks of the optical disk 1500and a reproduced signal of data recorded on the optical disk 1500. Thereproduced signal is demodulated by the signal process circuit 1304 soas to reproduce data. Further, both the focus error signal and thetracking error signal are input to the servo means 1306, and the servomeans 1306 controls the optical head 1302 so as to realize the optimallight focus state and track scanning state.

The tracking error signal is also input to the wobble signal extractioncircuit 1307, and the wobble signal extraction circuit 1307 extracts awobble signal from the tracking error signal on which a signal recordedin an address region is also superimposed according to a structure ofthe address region by means of a band-pass filter, which passes wobblecomponents therethrough, and a binarizing circuit.

The wobble cycle measurement means 1308 uses the reference clock at afixed frequency generated by the reference clock generation means 1310so as to measure a cycle of the wobble signal output by the wobblesignal extraction circuit 1307. The reference clock generation means1310 includes, for example, a quartz oscillator. Measurement of thewobble cycle can be realized, for example, using the reference clock soas to count the time period between one rise of the wobble signal andthe next rise. The substrate discrimination means 1309 observes a signaloutput by the wobble cycle measurement means 1308 so as to discriminatewhether the servo means is performing an operation on the first orsecond substrates.

The recording signal generation circuit 1312 generates a recordingsignal for recording data on the optical disk 1500. The optical head1302 records a recording signal generated by the recording signalgeneration circuit 1312 on either data region 1004 or 1104 of theoptical disk 1500.

Next, a flow of the substrate discriminating operation is described withreference to a flowchart of FIG. 21. Firstly, once the power of therecording/reproducing apparatus is turned on when the optical disk 1500is being inserted thereinto or in a state where the optical disk 1500has been inserted thereinto (S1401), the optical head 1302 is moved tothe vicinity of an innermost circumference of the data region, and themotor 1305 is rotated at a prescribed rotation speed so as to rotate theoptical disk 1500 (S1402). Next, the optical head is made to emit alaser beam (S1403), focus control is turned on so as to focus the laserbeam on the first or second substrate 901 or 905 (S1404). Further,tracking control is turned on so as to scan a groove track or a landtrack with the laser beam (S1405).

In this state, a signal including wobble components shown in FIG. 22appears in a tracking error signal. In FIG. 22, reference numeral 1501denotes a tracking error signal when the servo means is performing anoperation on the first substrate 901, and reference numeral 1503 denotesa tracking error signal when the servo means is performing an operationon the second substrate 905. In the wobble signal extraction circuit1307, the band-pass filter performs bandwidth limiting on the trackingerror signal so as to pass frequency bandwidth components of a wobblesignal therethrough, thereby removing the other bandwidth components.

By binarizing the tracking error signal after the extraction of thewobble components, a signal denoted by reference numeral 1502 or 1504 isobtained. Reference numeral 1502 denotes a signal when the servo meansis performing an operation on the second substrate, and referencenumeral 1504 denotes a signal when the servo means is performing anoperation on the first substrate. The wobble cycle measurement means1308 uses the reference clock so as to count wobble cycle 1505 or 1506(S1406). In this case, when the number of counts in the second substrate905 is 220 and the number of counts in the first substrate 901 is 160,the signal 1502 obtained from the second substrate is longer than thesignal 1504 obtained from the first substrate by 60 counts. Therefore,when a threshold is 190 counts, it is possible to determine that thefirst substrate is being operated on when the number of counts is equalto or more than 190 and the second substrate is being operated on whenthe number of counts is lower than 190 (S1407, S1408 and S1409).

It should be noted that in the case where the threshold of the countvalue is sufficiently large, even when the position on which a focusingor tracking operation of the servo means is performed is slightlydeviated, it is possible to perform the discriminating operation. Inthis manner, by setting the wobble cycles of the first and secondsubstrates so as to differ from each other, it is possible to increase adifference between the theoretical number of counts and a threshold,thereby increasing the reliability of discrimination.

In Embodiment 2, although the number of counts in the second substrate905 is 220 and the number of counts in the first substrate 901 is 160,the number of counts in both the first and second substrates is notlimited to this and the other number of counts can be employed so longas it is possible to discriminate as to on which layer the servo meansis performing an operation according to the difference in the number ofcounts.

Further, in Embodiment 2, although the number of counts in the secondsubstrate 905 is 220, the number of counts in the first substrate 901 is160 and the difference in the number of counts between them is 60, thedifference in the number of counts is not limited to this and thedifference in the number of counts can be changed to the other number solong as it is possible to discriminate as to on which layer the servomeans is performing an operation according to the change in thedifference in the number of counts.

Furthermore, when the amplitudes of the oscillation of the grooves aresubstantially equivalent, a higher amplitude of a reproduced signal isobtained at a lower frequency of the oscillation, and therefore as inthe case of Embodiment 2, by setting a wobble frequency of a substratelocated far from a surface which is irradiated with a laser beam so asto be lower than that of a substrate located near the surface, it ispossible to reduce a deterioration in a signal-to-noise ratio of thesignal 1501 obtained from the second substrate.

As described above, by providing the first and second substrates suchthat cycles of the oscillation of the tracks at start positions of theirrespective data regions are different from each other, it is possible todiscriminate between the first and second substrates at the time a focusor tracking operation is performed by the servo means, and thereforeeven when information representing which one of the first and secondsubstrates 901 and 905 is the substrate is recorded in the lead-inregions provided at the innermost circumference of the disk, it is notnecessary to reproduce such information so as to discriminate betweenthe first and second substrates 901 and 905. Therefore, it is possibleto shorten the time period required for reproducing data from thelead-in regions.

In this manner, by providing the first and second substrates 901 and 905such that cycles of the oscillation of the tracks at start positions oftheir respective data regions are different from each other, it ispossible to discriminate between the first and second substrates 901 and905 at the time a focus or tracking operation is performed by the servomeans, and therefore it is possible to shorten the time period requiredfor reproducing data recorded in the address region of the substrate onwhich the servo means is performing an operation.

It should be noted that according to the present invention, it is notnecessary to reproduce data recorded in the lead-in region or theaddress region so as to discriminate between the first and secondsubstrates 901 and 905, and it is possible to set the irradiation powerof a laser beam so as to be equal to or lower than the lowestirradiation power for reproducing data from the respective regions solong as the wobble polarities can be discriminated, thereby eliminatingthe risk of damaging data recorded in the data region or the addressregion.

In Embodiment 2, although an optical disk having two recording layers inwhich incident surfaces of readout light are identical to each other hasbeen described, the recording layers are not limited to two layers. Solong as at least two recording layers are available for recording, otherlayers may be used exclusively for reproducing.

Although pits are positioned in the address region according toEmbodiment 2, the positions, the number and the arrangement of the pitsmay not be limited to this.

Further, in Embodiment 2, although tracks are discontinuously provideddue to the address regions, the address regions 1003 and 1103 shown inFIG. 18 are not always required so long as the start positions of thetracks are identified, and the tracks can be discontinuously provideddue to regions except for the address regions.

Furthermore, in Embodiment 2, although the first and second substratesare not defined with respect to an oscillation amplitude of a wobble,the oscillation amplitude in the second substrate can be set so as to behigher than that in the first substrate. FIG. 23 shows an example ofsuch a case. As shown in FIG. 23, by setting an oscillation amplitude A4of the second substrate so as to be higher than an oscillation amplitudeA3 of the first substrate, it is possible to improve a signal-to-noiseratio of a wobble signal in the case where the servo means is performingan operation for controlling a light beam on the second substrate.

According to Embodiments 1 and 2, in the optical disks shown in FIGS.11, 12, 13 and 14, a recording operation is performed only on the groovetracks and in the optical tracks shown in FIGS. 4, 10, 15, 19 and 23besides the above-mentioned figures, a recording operation is performedon both the land tracks and groove tracks. However, tracks on which therecording operation is performed are not limited to this. In the opticaldisks shown in FIGS. 11, 12, 13 and 14, a recording operation can beperformed only on the land tracks, and in the optical tracks shown inFIGS. 4, 10, 15, 19 and 23 besides the above-mentioned figures, aconfiguration that a recording operation is performed on only one typeof track, i.e., address information is provided to only one type oftrack, can be employed.

Further, in Embodiments 1 and 2, although the tracks oscillatesinusoidally, the form of the oscillation is not limited to this. Anyform of the oscillation differing from the sinusoidal oscillation can beemployed so long as the oscillation is cyclical. FIG. 24 shows anexample of such a case. As shown in FIG. 24, track A becomes linear inperiods T1 in the vicinity of a phase at 180 degrees, track B becomeslinear in periods T2 in the vicinity of a phase at 0 degrees, and trackC becomes linear in both periods T1 in the vicinity of a phase at 0degrees and periods T2 in the vicinity of a phase at 180 degrees. Withrespect to these tracks, as shown in FIGS. 25, 26 and 27, although it ispossible to discriminate recording layers (first and second layers) bydetecting the phases in the above-described manner, as shown in FIG. 28,a different track pattern can be employed for each of the recordinglayers (first and second layers) while keeping uniform phases. In trackA where edges become sharp in a phase at 180 degrees and track B whereedges become sharp in a phase at 0 degrees, the polarity at the edgeportions are inversed, f or example, when a tracking signal isdifferentiated, thereby identifying the patterns.

Furthermore, in FIG. 10, although patterns corresponding to the codes“S”, “0” and “1” are provided in each address region using pits, thepresent invention is not limited to this. Patterns can be provided inthe tracks, rather than the address regions, for example, such that onetrack corresponds to the code “S”, another track corresponds to the code“0” and still another track corresponds to the code “1”. By providingthe tracks so as to correspond to the codes, the necessity for providingthe address regions in which the patterns corresponding to the codes“S”, “0” and “1” are provided using the pits is removed, and thereforeit is possible to provided less address regions, thereby increasing thecapacity of an optical disk.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, it is possibleto readily discriminate between first and second substrates at the timea focus or tracking operation is performed by the servo means, andtherefore even when there is data about a layer in a lead-in regionprovided at the innermost circumference of a disk, it is not necessaryto reproduce such data, whereby it is possible to shorten the timeperiod required for reproducing data from the lead-in region.

Further, according to the present invention, it is possible to readilydiscriminate between the first and second substrates at the time a focusor tracking operation is performed by the servo means, and therefore itis possible to shorten the time period required for reproducing datafrom an address region of a substrate on which a servo means isperforming an operation.

Furthermore, according to the present invention, it is not necessary toreproduce data from the lead-in region or the address region so as todiscriminate between the substrates, and it is possible to set theirradiation power of a laser beam so as to be equal to or lower than thelowest irradiation power for reproducing data from the respectiveregions so long as wobble polarities can be discriminated, therebyeliminating the risk of damaging data at the data region or the addressregion in a recording region.

Further still, by employing combinations of the embodiments of thepresent invention, it is possible to improve precision in discriminationof the substrates.

1. An information recording medium including a plurality of layers,wherein a first layer of the plurality of layers has a first track, asecond layer adjacent to the first layer of the plurality of layers hasa second track, the first track includes a first shape, the second trackincludes a second shape, and the first shape and the second shape aredifferent from each other.
 2. A reproducing controlling apparatus forcontrolling data reproduction from an information recording mediumincluding a plurality of layers, wherein a first layer of the pluralityof layers has a first track, a second layer adjacent to the first layerof the plurality of layers has a second track, the first track includesa first shape, the second track includes a second shape, and the firstshape and the second shape are different from each other, thereproducing controlling apparatus comprising; a discriminator, fordiscriminating whether the reflection light is light reflected from thefirst layer or light reflected from the second layer, based on a signalequivalent to the first shape or the second shape extracted from atracking error signal generated based on an electrical signalcorresponding to reflected light from one of the first layer and thesecond layer of the information recording medium, wherein thediscriminator delivers the discriminated result to a means forinstructing reproduction of the information recording medium.
 3. Areproducing controlling method for controlling data reproduction from aninformation recording medium including a plurality of layers, wherein afirst layer of the plurality of layers has a first track, a second layeradjacent to the first layer of the plurality of layers has a secondtrack, the first track includes a first shape, the second track includesa second shape, and the first shape and the second shape are differentfrom each other, the reproducing controlling method comprising;discriminating, based on a signal equivalent to the first shape or thesecond shape extracted from a tracking error signal generated based onan electrical signal corresponding to reflected light from one of thefirst layer and the second layer of the information recording medium,whether the reflection light is light reflected from the first layer orlight reflected from the second layer; and delivering the discriminatedresult to a means for instructing a reproduction of the informationrecording medium.
 4. A recording controlling apparatus for controllingdata recording on an information recording medium including a pluralityof layers, wherein a first layer of the plurality of layers has a firsttrack, a second layer adjacent to the first layer of the plurality oflayers has a second track, the first track includes a first shape, thesecond track includes a second shape, and the first shape and the secondshape are different from each other, the recording controlling apparatuscomprising; a discriminator, for discriminating whether the reflectionlight is light reflected from the first layer or light reflected fromthe second layer, based on a signal equivalent to the first shape or thesecond shape extracted from a tracking error signal generated based onan electrical signal corresponding to reflected light from one of thefirst layer and the second layer of the information recording medium,wherein the discriminator delivers the discriminated result to a meansfor instructing recording to the information recording medium.
 5. Arecording controlling method for controlling a data recording on aninformation recording medium including a plurality of layers, wherein afirst layer of the plurality of layers has a first track, a second layeradjacent to the first layer of the plurality of layers has a secondtrack, the first track includes a first shape, the second track includesa second shape, and the first shape and the second shape are differentfrom each other, the recording controlling method comprising;discriminating, based on a signal equivalent to the first shape or thesecond shape extracted from a tracking error signal generated based onan electrical signal corresponding to reflected light from one of thefirst layer and the second layer of the information recording medium,whether the reflection light is light reflected from the first layer orlight reflected from the second layer; and delivering the discriminatedresult to a means for instructing recording to the information recordingmedium.